It is known to aerate a mix for the preparation of an ice cream through the use of an aerating means comprising a rotating element that fits into the barrel of a continuous ice cream freezer. This aerating means is commonly referred to as a dasher. On rotation the dasher imparts mechanical energy into the mix in order to achieve aeration and generate a fat network by aggregating some of the fat droplets. This aggregation is necessary for product stability.
For many industrial continuous freezers there are a variety of dasher types available. These can be differentiated from each other by the volume displaced within the freezer barrel which can be assessed by simply filling the freezer barrel with a liquid, such as water, and measuring the volume of liquid displaced when the dasher is fitted therein. A dasher described as a series 80 indicates that this rotating element occupies 80% of the available internal volume of the freezer barrel so that only 20% of the space is available to be occupied by the mix to be aerated. By contrast a series 15 dasher, also known in the art, demonstrates a displacement volume of only 15% of the internal barrel volume, the remaining 85% being available to be occupied by a mix to be aerated.
In conventional ice cream processing it is generally accepted that higher displacement dashers such as the series 80 give rise to high quality ice cream being highly churned (Ice Cream 5th Edition, W. S. Arbuckle et al., page 183) thus showing optimal levels of fat de-stabilisation, while at the same time product dryness, good meltdown resistance and product hardness. These displacement dashers are therefore the standard form of aerating means used in ice cream manufacture.
Cold extrusion of aerated compositions is also known in the art. U.S. Pat. No. 5,345,781 describes the extrusion of a pre-aerated foam through a freezing device. Pre-aeration has conventionally been undertaken through the use of an aerating means in the form of a high displacement dasher (Ice Cream 5th Edition, W. S. Arbuckle et al., page 184). The foam once aerated is then transferred to cold extrusion apparatus. FIG. 3 of U.S. Pat. No. 4,345,781 illustrates this approach.
Cold extrusion allows a convenient and preferred means of preparing ice cream, however this freezing route has been found by the applicants to present additional processing problems with particular formulations that contain a high ratio of liquid to solid fat at the processing temperature. The applicants when applying the conventionally combination of an aeration means with 80% displacement and cold extrusion apparatus, have observed an inability to achieve desired levels of overrun (>90%). This loss of overrun can be so severe as to give rise to phase separation and the loss of control of the process to the extent that extrusion apparatus may become blocked.
The ice cream formulations prepared by conventional aeration and cold extrusion systems comprise a fat phase with a relatively high melting point. This means that little if any liquid fat is present at the processing temperature.
The applicants have identified a need to extend the range of fats that can be applied to ice cream manufacture. In particular there is a need for the development of novel ice cream compositions which have formulations that can comprise a fat component having a lower melting point, thus imparting a higher level of liquid fat in the fat phase at the processing temperature. At the same time formulations must maintain the high degree of stable aeration and low levels of destabilised fat and overrun loss characteristic of conventional ice creams. The ability to use increasingly varied fats would also allow the manufacture of ice cream at a reduced cost.
The technical problem to be solved by the present invention therefore relates to the production of novel ice cream formulations, wherein said formulations comprise fat types that have not been conventionally applied to commercial ice cream manufacture due to high levels of liquid fat that they impart in the fat phase of a mix at the processing temperature. More particularly the problem has been found to particularly relate to enabling the cold extrusion of these so mentioned novel ice cream formulations.
It has been surprisingly been found that a solution to this problem resides in the use of equipment which has never been used for this type of formulation before. There is no suggestion in the prior art that this type of equipment has any positive influence on the destabilisation of fat, phase separation or overrun loss during the processing of a composition.
The present invention seeks to provide a stable composition with at least 90% overrun, wherein said composition comprises a fat phase which has a high ratio of liquid fat to solid fat at the processing temperature. More particularly the present invention provides aerated novel compositions of this type which are also suitable for cold extrusion.
Tests and Definitions
Levels of liquid fat can be determined by 13C-NMR spectroscopy wherein the liquid fat level of an emulsion of an ice cream mix of the invention is determined.
Measurements carried out at −5 & +50° C. for 100% fully liquid state. 13C-NMR is carried out on a Bruker AMX-400 high resolution NMR spectrometer, with 10 mm sample tubes. Data is acquired with inverse gated proton de-coupling and suitable interscan delay to ensure quantitative results. Volume of samples for 100% liquid measurement was reduced to keep total sample within probe coils and hence negate any complications due to premix separation. Measurements at −5° C. is carried out after external equilibration for at least 2 hrs. 100% liquid measurements is carried out after at least 30 min equilibration, at +50° C., in spectrometer probe. All temperatures verified using external thermocouple meter. Liquid fat content is determined by integration of fat signals (15-40 ppm), relative to integral of sugar signals (60-85 ppm). At −5° C. and above the integral of sugar signals will remain constant and hence can be used as an internal standard. The proportion of liquid fat at the chosen temperature is calculated by comparison of integrals with those from fat signals from the 100% “melted” sample.
For the purpose of the invention overrun can be determined as described in Ice Cream 4th Edition, Arbuckle et al., page 181.
Cold extrusion (coldex) is used to denote a cooling system wherein a material enters extrusion apparatus a temperature which is somewhat higher than that at the point of extrusion. Typically in the cold extrusion of ice cream material enters the extrusion apparatus at about −13° C. and subsequently about −18° C. at the point of extrusion.